Computing systems, including servers, local networks, or regional and global networks, often require the interconnection of a number of computing units. For example, some electronic systems, such as servers, include a number of printed circuit boards placed into a blade server or rack server. The boards are typically equipped with connectors that allow them to attach to corresponding connectors on a backplane. Electrical interconnection among the boards is thereby provided by the backplane, allowing the exchange of information between the boards.
This approach has its limitations, however. With increasing data bandwidths required between servers, blades, or cards, backplanes capable of accommodating them become not only more expensive, but more complex and therefore less robust and reliable. Other such complex platforms include multi-core computers, computer clusters, and supercomputers. Each of these applications requires fast, high-bandwidth interconnections between computing units (processor cores, processors, or processor platforms) that also allows for input/output architecture capable of supporting high-speed computing. Such arrangements can involve thousands of individual computing nodes.
Directing data among such large networks can involve a tremendous number of time- and resource-consuming routing steps. For example, packet switching can involve queuing-related delays. On the other hand, optical interconnects provide the potential for very high bandwidths while providing generally less electromagnetic interference generation and susceptibility than electrical interconnects. However, optical communication between units generally involves converting data from electrical signal to a light signal and back. To minimize the limitations of routing and data conversion while maintaining a high degree of interconnection, it is desirable to directly connect as many units in a network to as many other units as possible. Unfortunately, for larger networks this can require large numbers of optical cables, adding to costs and making the system difficult to maintain.